1. Field of the Invention
This invention generally relates to a ball grid array package, and more particularly to a ball grid array package having a plurality of partitioning walls for keeping solder balls in proper position.
2. Description of the Related Art
Miniaturization of semiconductor device size has been an important topic in the art, when the device requires more I/O pins along with the increase of device density. Relatively, the ball grid array (BGA) package is an efficient packaging technology since it can provide more I/O pins.
Referring to FIG. 1, it shows a conventional ball grid array (BGA) package 10 using wire bonding technique and being disposed on a main board 30. The BGA package 10 includes a substrate 20, a chip 11, and a plurality of solder balls 40. The substrate 20 has an upper surface 22, a lower surface 24 opposite to the upper surface 22, and a plurality of metal wirings (not shown). The chip 11 is disposed on the upper surface 22 of the substrate 20 and electrically connected to the metal wirings of the substrate 20 by a plurality of bonding wires 12. The solder balls 40 are disposed on the lower surface 24 of the substrate 20 and electrically connected to the chip 11 through the metal wrings and the bonding wires 12.
Referring to FIGS. 2 and 3, in manufacturing processes of the BGA package 10, a solder mask 26 is provided on the lower surface 24 of the substrate 20 and a plurality of pads 50 are exposed therefrom. A plurality of flux units 60 are applied to the pads 50. Then, the solder balls 40 are disposed on the flux units 60 and adhered to the pads 50 (as shown in FIG. 3) by a reflow process.
After the solder balls 40 pass through the reflow process, a solder bridge formed between two pads 50 as shown in FIG. 3 might be occurred due to the spread of the flux units 60. Further, in manufacturing and/or transporting processes, the solder balls 40 may also be shifted due to the occurrence of a shake, a vibration and so on such that the implantation yield of the solder balls 40 is reduced.
For example, U.S. Pat. No. 5,636,104 discloses a BGA package using wire bonding technique, which is incorporated herein by reference. The substrate of such a BGA package comprises a plurality of groove mounting pads for carrying a plurality of solder balls, thereby improving the strength and the positioning capability of the solder balls on the substrate. However, the plurality of groove mounting pads will increase the manufacturing processes and cost.
Accordingly, there exists a need to provide a BGA package which can improve the positioning capability and increase the implantation yield of the solder balls.